After sending this I realized that XFS doesn't support journal=data... I
thought journal=data was a general VFS part of the linux kernel... my
bad. :)
I guess you are just left with in kernel tuning (someone previously
posted a link to).
Bryan Whitehead wrote:
If you are so concerned with the awesomeness of XFS's caching... why
not turn on data-journaling? Then data (not just meta-data) is
committed to the journal.
You can also tune XFS to not wait so long to hold cached data.
Alan McKinnon wrote:
On Saturday 28 October 2006 16:41, b.n. wrote:
Dale ha scritto:
If you use XFS, make sure you have good power. XFS does not like
power failures at all. I have had to reinstall on a second rig
because of this very problem. If you have a UPS, that may be OK.
Thanks a lot for the advice. Power outages do happen and I don't have
an UPS. Why does it happen? Isn't XFS journaled?
Yes it is journaled but it also allows data to be very aggressively
cached. Make that VERY aggressively cached. With the result that data
can be held in a huge cache somewhere and the kernel can be convinced
it has been written to disk.
Consider XFS's pedigree - SGI wrote it for their graphics machines.
These were big monsters backed up with high grade UPSs and such - the
logic was that if you spend a brazillion bucks on hardware, a mega
UPS is part of the deal, along with the wages to pay the army of
admins you also need.
And, when doing video rendering, it turns out that it's easier to
simply re-render a frame when the filesystems does something odd with
the data rather than go to the effort of writing an FS that is 100%
reliable. So SGI sacrificed something that doesn't actually matter
for their use case to gain a significant performace increase (which
does matter a great deal)
alan
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